In electronic appliances such as mobile telephones or handheld computers (PDAs), it is necessary to ensure data transmission between a circuit board of the screen, which is mechanically connected to a base part via an articulated joint, and a circuit board assigned to the keypad/keyboard. This data transmission is typically effected electronically via ribbon cables and/or coaxial cables, but this entails the disadvantages of comparatively large dimensions, EMC problems and a considerable susceptibility to wear.
A known device makes use of the possibility of optical data transmission between two structural units connected to one another by an articulated joint. For this purpose, an optical articulated joint is provided, which comprises two structural units which are produced from a material suitable as optical waveguide and can be rotated relative to one another about an axis of rotation. The two structural units have mirror-coated surfaces in order to ensure the guidance of the light signal. Between the two structural units there is an air gap which the light signal has to cross.
One disadvantage of the known device is the complicated free radiating optical arrangement, which requires special materials for the two structural units, and also a precise and primarily also permanent alignment. Such a permanent exact alignment cannot be reliably ensured, however, in the case of a highly stressed object of practical use such as a mobile telephone, so that the device is not expected to exhibit an appreciably improved service life in comparison with devices having ribbon cables. Moreover, the known device has focusing problems or reflecting problems occurring at the entrance and exit of the light signal at the air gap. These problems can only be solved with considerable outlay and are therefore associated with disproportionate costs.